Effect of microencapsulated plant extracts on mosquito repellency

Abstract

Mosquitoes are the most important single group of insects in terms of public health importance. Mosqui-toes not only cause nuisance by their bites but also transmit deadly diseases. The activity of mosquitoes is affected by climate, light and temperature. In tropical areas like India, the population of mosquitoes is found huge day by day. Repeated use of synthetic insecticides for mosquito control has disrupted environment as well as human health. To overcome this problem, plant derived compounds may be the better alternate over synthetic insecticides. To enhance the health and hygiene qualities by means of use of medicinal plants through effective application technique on textiles, marigold (petals) and nirgundi (leaves) methanol extract was used as mosquito repellent finish on 100 % woven cotton. For applying mosquito repellent finish on fabric, complex coacervation technique of microencapsulation was used through pad-dry-cure method. Finished cotton samples were tested against Anopheles stephensi by using laboratory cage method for their efficacy and durability to washing and sun-drying as per standard test methods. Marigold (petals)and nirgundi (leaves) extract finished fabric samples showed 96 and 94 % repellency respectively after 60 minutes of observation. It remained 56 % and 54 % (after 15 washes) and 54 and 52 % (after expo-sure in sun for 3 hours) by the application of marigold and nirgundi extracts respectively. Hence, microencapsulation technique on selected cotton textile proved effective to repel mosquitoes up to acceptable level according to WHO (1996).